That’s a really tough one—there are so many pieces I love and never get tired of hearing—but certainly high on the list is “LENTO SOSTENUTO TRANQUILLO MA CANTABILE”
from Symphony No. 3 (“Symphony of Sorrowful Songs”)
by Gorecki, with passages sung by Dawn Upshaw.

It’s used in the final minutes of the film “Fearless” with Jeff Bridges.
Reduces me to a puddle every time I hear it.

Here’s another one… it’s called “Are You Going With Me?” by Pat Metheny. The first time I heard this back in the ‘80s I had to pull off the road and listen. Took me months to find out who the artist was. In those days, didn’t have that amazing iPhone App that identifies music on the radio.

My answer is multi-layered, so bear with me. I love all kinds of music, but for me, the most beautiful piece of music I’ve ever heard is John William’s soundtrack to the Star Wars movies. Each movie has its own theme and even the Imperial March is gorgeous. My favorite piece however is Across the Stars, which is the love theme. I just thought it was utter gorgeousness.

@serafina – There are umpteen metal songs that start off with dark-dissonant-“beautiful” melody – in contrast for heavier things to come; or entire such songs as contrast to the rest of the album. (Kind of like a ballad stuck in the middle of an Ozzy record – artistic/dramatic contrast.)